Upgrading MySQL databases after a software update

Sometimes MySQL changes its internal database structures between versions. When that is the case, you might get these kind of errors after updating it (probably via yum) and trying to start it:[ERROR] Missing system table mysql.proxies_priv; please run mysql_upgrade to create it
...
[ERROR] Native table 'sometable'.'something' has the wrong structure

Additionally, trying to perform certain operations on the databases (like dumps) may throw out this error:Cannot load from mysql.proc. The table is probably corrupted

The solution is rather simple and involves running the mysql_upgrade program:

# mysql_upgrade -u root -p

and enter your root password at the next prompt. If all goes well, the errors should go away.

If something failes, try running it one more time with

# mysql_upgrade -u root -p --force

If you still having problem with other tables, no matter what (InnoDB or MyISAM) you can refer here to repair MyISAM table or InnoDB.